Carbon dioxide-independent and -dependent components of light inhibition of the conversion of 1-aminocyclopropane-1-carboxylic acid to ethylene in oat leaves

Light inhibits while carbon dioxide enhances the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene in oat ( Avena sativa L. cv. Victory) leaf segments. The possibility that the light inhibition is mediated through changes of carbon dioxide has been investigated. The level of CO₂ increases or decreases in the sealed incubation vial in darkness or in light, respectively, which can apparently account for the differences in ACC-dependent ethylene production between the dark and light treatments. However, although the evolution of ethylene from ACC in the dark is reduced upon depletion of CO₂, the difference between light and dark is still very noticeable. Moreover, the production of the ethylene in CO₂-free air in the dark was still higher than in the light, where the concentration of CO₂ was 0.01%. It is proposed that the light effect on the conversion of ACC to ethylene is composed of two distinguishable components: one CO₂-mediated and the other CO₂-independent.